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Abstract:

A system is provided projecting a three-dimensional image. The system
includes a first light source, the first light source emitting light in a
first direction. A second light source is provided, the second light
source emitting light in a second direction, the second direction being
opposite the first direction. A beam splitter device is disposed between
the first light source and the second light source to receive light from
the first light source and the second light source, the beam splitter
device being arranged to rotate about an axis. An LCoS image device is
disposed adjacent the beam splitter device, the LCoS image device having
an image surface arranged substantially perpendicular to the first
direction and the second direction.

Claims:

1-9. (canceled)

10. A system comprising: a first light source, the first light source
emitting light in a first direction; a second light source, the second
light source emitting light in a second direction, the second direction
being opposite the first direction; a beam splitter device disposed
between the first light source and the second light source to receive
light from the first light source and the second light source, the beam
splitter device being arranged to rotate about an axis; and, a LCoS image
device disposed adjacent the beam splitter device, the LCoS image device
having an image surface arranged substantially perpendicular to the first
direction and the second direction.

11. The system of claim 10 further comprising a projection lens adjacent
the beam splitter device opposite the LCoS image device, the projection
lens positioned to receive light reflected from the LCoS image device.

12. The system of claim 11 further comprising: a first fly's eye lens
arranged between the first light source and the beam splitter device;
and, a first pre-polarizer lens arranged between the first fly's eye lens
and the beam splitter device.

13. The system of claim 12 further comprising: a second fly's eye lens
arranged between the second light source and the beam splitter device;
and, a second pre-polarizer lens arranged between the second fly's eye
lens and the beam splitter device.

14. The system of claim 10 further comprising a feedback circuit coupled
to the first light source, the second light source, the beam splitter
device and the LCoS image device, the feedback circuit providing a
modulation signal to the first light source and the second light source,
wherein the beam splitter device rotates at two times a frequency of the
modulation signal.

15. The system of claim 13 wherein the first light source comprises: a
plurality of first LED devices; a plurality of first light collection
optics, each of the plurality of first light collection optics associated
with one of the plurality of first LED devices; and, a first dichroic
color combiner disposed between the plurality of first light collection
optics, the first dichroic color combiner arranged to direct light from
the plurality of first LED devices into the first fly's eye lens.

16. The system of claim 15 wherein the second light source comprises: a
plurality of second LED devices; a plurality of second light collection
optics, each of the plurality of second light collection optics
associated with one of the plurality of second LED devices; and, a second
dichroic color combiner disposed between the plurality of second light
collection optics, the second dichroic color combiner arranged to direct
light from the plurality of second LED devices into the second fly's eye
lens.

17. The system of claim 10 wherein the first light source, the second
light source, the LCoS image device and the beam splitter are arranged
within a space 5-10.5 mm in height, 20-37 mm in width and 20-37 mm in
length.

18. The system of claim 10 wherein the first light source, the second
light source, the LCoS image device and the beam splitter use less than
or equal to 30 milliwatts.

19. A projector system for a portable electronic device comprising: a
first light source arranged to direct light in a first direction; a
second light source arranged to direct light in a second direction, the
second direction being 180 degrees from the first direction; a beam
splitter device arranged to rotate on an axis, the axis being
substantially perpendicular to the first direction and the second
direction; and, an imaging device adjacent the beam splitter device.

20. The system of claim 19 wherein the beam splitter device is
substantially equidistant from the first light source and the second
light source.

21. The system of claim 20 further comprising a projection lens arranged
adjacent the beam splitter device opposite the imaging device.

22. The system of claim 21 wherein the imaging device is a LCoS image
device.

23. The system of claim 19 further comprising: a feedback device coupled
to communicate with the first light source, the second light source, the
beam splitter device and the imaging device, the feedback device
providing a modulation signal having a modulation frequency; and, wherein
the beam splitter device rotates at substantially two times the
modulation frequency.

24. The system of claim 23 wherein the beam splitter device rotates at a
constant speed.

25. The system of claim 23 wherein the beam splitter device rotates at a
variable speed.

Description:

BACKGROUND

[0001] The present invention relates to a stereoscopic three dimensional
image projector, and more specifically, to a small three dimensional
projector usable with passive glasses.

[0002] Three dimensional (3D) movies and pictures have become a popular
form of entertainment due to the increased realism of the images. 3D
images utilize the human physical trait of binocular vision. Human eyes
are spaced about 2 inches (5 centimeters) apart, therefore each eye sees
the world from a slightly different perspective. The brain receives both
images and has a binocular vision function that correlate the difference
between what each eye sees to determine distance. The determination of
the distance provides the three-dimensional effect that a person sees.

[0003] To create a binocular image on a two dimensional surface, such as a
movie or television screen, the user typically wears glasses. The glasses
alter the way that the user views the images to create the simulated 3D
effect. Typically there are two types of glasses, passive glasses and
active glasses. The type of glasses used will depend on the type of image
projection system being used.

[0004] Passive glasses rely upon an optical effect created by using
different lenses for each eye. The projection system emits a sequential
series of images where subsequent images are slightly offset. The images
are arranged such that the user sees the first image through a first lens
of the glasses (e.g. the right eye) and the second image is seen with the
other lens (e.g. the left eye). Since the images are projected quickly,
the user does not notice the multiple images, but rather sees a three
dimensional effect. Originally, passive glasses used different color
lenses to filter out images, however this limited the use of 3D images
when full color images are desired. To alleviate this issue, polarized
lenses were developed where each lens of the glasses allowed the
transmission of different polarized light. The polarized passive lenses
allowed for full color 3D images to be transmitted. Passive lenses are
more common with projector type systems, such as movie theaters for
example, where multiple projectors may be used to project the images on a
screen.

[0005] The development of 3D television systems created a new challenge as
there typically isn't enough room for multiple projectors. To accommodate
this, active lenses were created. With an active lens, the glasses
wirelessly communicate with the projector to synchronize the glasses
operation with the images being displayed. With active glasses, the
lenses are typically liquid crystal displays that can switch between
transmitting light and blocking light. In this way, the glasses may
rapidly switch the left and right lenses between clear and opaque. While
the glasses are switching, the television is projecting a series of
sequential images. When this switching is synchronized between the
television and the glasses, the user experiences a three dimensional
effect.

[0006] Accordingly, while existing three dimensional projectors are
suitable for their intended purpose a need for improvement remains,
particularly in providing a system with a single projector that can
project images viewable with passive glasses.

SUMMARY

[0007] According to one embodiment of the invention, a method is provided
having a first light source, the first light source emitting light at a
first polarization. A second light source is provided opposite the first
light source, the second light source emitting light at a second
polarization. A liquid crystal on silicone (LCoS) image device is
provided. A beam splitter device is provided between the first light
source and the second light source adjacent the LCoS image device. The
beam splitter device is rotated. A first light is emitted from the first
light source. The first light is reflected with the beam splitter device
onto the LCoS image device. A second light is emitted from the second
light source after the first light is emitted. The second light is
reflected with the beam splitter device onto the LCoS image device.

[0008] According to another embodiment of the present invention, a system
is provided having a first light source, the first light source emitting
light in a first direction. A second light source is provided, the second
light source emitting light in a second direction, the second direction
being opposite the first direction. A beam splitter device is disposed
between the first light source and the second light source to receive
light from the first light source and the second light source, the beam
splitter device being arranged to rotate about an axis. A LCoS image
device is disposed adjacent the beam splitter device, the LCoS image
device having an image surface arranged substantially perpendicular to
the first direction and the second direction.

[0009] According to another embodiment of the present invention, a
projector system for a portable electronic device is provided. The
projector system includes a first light source arranged to direct light
in a first direction. A second light source is arranged to direct light
in a second direction, the second direction being 180 degrees from the
first direction. A beam splitter device is arranged to rotate on an axis,
the axis being substantially perpendicular to the first direction and the
second direction. An imaging device is arranged adjacent the beam
splitter device.

[0010] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects of the
invention are described in detail herein and are considered a part of the
claimed invention. For a better understanding of the invention with the
advantages and the features, refer to the description and to the
drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0011] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at the
conclusion of the specification. The forgoing and other features, and
advantages of the invention are apparent from the following detailed
description taken in conjunction with the accompanying drawings in which:

[0012]FIG. 1 is a schematic view of a three-dimensional image projector
in accordance with an embodiment of the invention;

[0013]FIG. 2 is a flow chart for a method of operating a
three-dimensional image projector in accordance with an embodiment of the
invention; and,

[0014] FIG. 3 is a flow chart for another method of operating a
three-dimensional image projector in accordance with another embodiment
of the invention.

DETAILED DESCRIPTION

[0015] Contemporary three-dimensional (3D) image projectors that use
passive glasses have typically use two projectors. Previous efforts to
use only a single projector rely upon an active lens within the projector
that switches between the sequential images. It should be appreciated
that substantial costs may be involved in using redundant projectors or
having a costly active lens. Further, these techniques do not scale well
as users desire comparable performance from smaller and smaller projector
packages.

[0016] A second type of projector uses active glasses having a liquid
crystal diode (LCD) lens that coordinates with the projector (typically a
television). The active glasses alternately block one of the lenses such
that the user will see sequential images through alternating lenses.
While active glasses perform well to create the 3D effect for the user,
they also have some less desirable characteristics. The active glasses
require an energy source such as a battery that needs to be periodically
recharged or replaced. If the communication between the television and
the glasses is interrupted, the 3D effect may be lost. Further, due to
the complexity of the system, the active glasses tend to be much more
costly.

[0017] With reference now to FIG. 1, a three dimensional projector 20 is
shown for projecting a three dimensional (3D) image from a single
projection lens in accordance with an embodiment of the invention. The
projector 20 includes a first light source 22 and an opposing second
light source 24. The light sources are arranged to direct light towards
each other. In other words, the direction of light from first light
source 22, indicated by arrow 26 is substantially 180 degrees apart from
the light emitted by light from second light source 24 as indicated by
arrow 28. In the exemplary embodiment, each light source includes three
monochromatic light emitting diodes (LED), a red LED 30, a green LED 32
and a blue LED 34. The LED's 30, 32, 34 are arranged to form three sides
of a square and direct light toward the center of light source 22, 24.
Each LED 30, 32, 34 may be coupled to direct light into a light
collection optic 36.

[0018] The light collection optic 36 directs the light from the LED's 30,
32, 34 into a dichroic color combiner 38. The dichroic color combiner 38
combines light from the LED's to create a desired light color. The light
from the first light source 22 exits via an open side 40 and passes
through a fly's eye lens 42 and a pre-polarizer lens 44. The fly's eye
lens 42 consists of an array of lenslets that have the effect of breaking
the transmitted light into many components and projecting them evenly
over the field of view. The result is even, bright illumination without
any reduction in light intensity at the periphery of the projected light.
The pre-polarizer lens 44 changes the polarization of the outgoing light
to have a desired polarization characteristic that is suitable for the
imaging device being used. Once the light leaves the pre-polarization
lens 42, the light passes through a focusing lens 52 that focus' the
light into a polarizing beam splitter 54 (PBS).

[0019] Similar to the first light source 22, the light from the second
light source 24 leaves an open side 46 and enters a fly's eye lens 48 and
a pre-polarization lens 50. After being conditioned by these lenses 48,
50, the light passes through a focusing lens 56 before entering the PBS
54.

[0020] A PBS 54 is an optical component that splits incident light rays
into a first (transmitted) polarization component and a second
(reflected) polarization component. In the exemplary embodiment, the PBS
54 is a device arranged to rotate about an axis 58. The PBS 54 has a
surface 60 that alternately reflects the light from the light sources 22,
24 as it rotates onto an imaging device 62. The light reflects off of the
imaging device 62 with a polarization that then substantially transmits
through the PBS 54 and out of the projector 20.

[0021] In one embodiment, the light sources 22, 24 are arranged
substantially the same distance (equidistant) from the PBS 54. This
provides advantages in that the light from each source will travel along
a substantially the same path length to project the image from the
projector 20. This simplifies the modulation of the light sources 22, 24
to the polarizing beam splitter.

[0022] In the exemplary embodiment, the imaging device 62 is a liquid
crystal on silicone (LCoS) type device that has an imaging surface 64
adjacent the PBS 54. In operation, the light from a lighting source 22,
24 reflects off the surface 60 onto the imaging device 62 which reflects
the light back through the PBS 54 and into a projection lens assembly 66
and out of the device 20. The use of an LCoS image device 62 provides
advantages in that the LCoS device 62 inherently polarizes the reflected
light.

[0023] In some embodiments, it should be appreciated that the combination
of the light sources 22, 24, PBS 54 and LCoS device 62 provide advantages
in reducing the size of the projector into the category of a
pico-projector or micro-projector. These small projectors may be suitable
to be used in a portable electronic device, such as but not limited to a
cellular phone, a tablet computer, a laptop computer, and a hand-held
gaming device for example. Embodiments of the present invention may also
be used in non-portable devices, such as but not limited to a desktop
computer or a television for example. In one embodiment, the projector 20
may be contained within a housing 5-10.5 mm×20-37 mm×20-37
mm.

[0024] The projector 20 may also include an optional feedback circuit 68.
The feedback circuit 68 is electrically coupled to communicate with the
first light source 22, the second light source 24, the PBS 54 and the
LCoS image device 62. The feedback circuit 68 provides a modulation
signal to the light sources 22, 24, to keep the light sources and LCoS
device 62 synchronized during operation. In other words, the feedback
circuit 68 ensures that the desired light source 22, 24 is emitting light
that corresponds to the image being displayed on the image surface 64. In
the exemplary embodiment, the PBS 54 rotates at a speed two times the
frequency of the modulation signal. In one embodiment, the projector 20
consumes 30 milliwatts or less electrical power during operation.

[0025] Referring now to FIG. 2, a method 70 is shown for operating a three
dimensional image projector, such as projector 20 for example. The method
70 starts in block 72 with rotating the PBS 54. The method 70 then emits
a light from a first light source in block 74, such as light source 22
for example. The light from the first light source reflects off of the
PBS 54 and onto an imaging device, such as LCoS imaging device 62 for
example. The light is reflected off of the imaging device and through one
or more lenses 66 to project an image N out of the projector 20 in block
76. Sequentially the second light source, such as light source 24 for
example, emits a light in block 78 which is reflected off of the PBS 54
and onto the imaging device. The light reflects off of the imaging device
and is projected out of the projector 20 in block 80. The method 70 then
loops back to block 74 to continue projecting images from the projector
20. It should be appreciated that the image N and the image N+1 are
similar but slightly offset to create a three-dimensional effect for a
user wearing polarized passive glasses.

[0026] Referring now to FIG. 3, another embodiment of a method 82 is shown
for operating a three dimensional image projector, such as projector 20
for example. The method 82 begins in start block 84 and proceeds to block
86 where a polarizing beam splitter, such as PBS 54 for example, is
rotated. The polarizing beam splitter may be rotated at a constant speed
or at a variable speed. The method 82 then proceeds to block 88 where the
light sources, such as light sources 22, 24 for example, receive a
modulation signal to synchronize the timing of light being emitted from
the light sources with the polarizing beam splitter. An image "N" is
created on an imaging device in block 90. Light is emitted from the first
light source in block 92. This first light is distributed, such as with a
fly's eye lens in block 94 and directed through a pre-polarizing lens in
block 96. This first light is reflected off of the polarizing beam
splitter onto the imaging device in block 98. The first light reflects
the image off of the imaging device and through a projecting lens to emit
the image N from the projector in block 100.

[0027] The method 82 then proceeds to block 102 where an image N+1 is
created on the imaging device. The second light source is activated in
block 104 to emit light. This second light is then distributed with a
lens, such as a fly's eye lens for example, in block 106 and a lens
pre-polarizes the second light in block 108. The second light is then
reflected off of the polarizing beam splitter and onto the imaging device
in block 110. The light reflecting off of the imaging device is polarized
with a polarization that is different from the first light reflected from
the imaging device. The second reflected light is transmitted through the
projecting lens to emit image N+1 from the projector in block 112. It
should be appreciated that the image N and the image N+1 are similar but
slightly offset to create a three-dimensional effect for a user wearing
polarized passive glasses.

[0028] In one embodiment, the polarizing beam splitter is rotated at a
constant rotational speed. This provides advantages and simplifies the
modulation of the light sources since once the light sources and
polarizing beam splitter are synchronized, the modulation signal may not
be needed. In another embodiment, the rotational speed of the polarizing
beam splitter may be varied or staggered. In one embodiment, the rotation
of the polarizing beam splitter may be stopped during operation. This
provides advantages in reducing the power consumption of the projector
and may further allow a two-dimensional image to be emitted using only
one of the light sources.

[0029] Embodiments of the present invention provide for a small, reliable
three-dimensional projector. Embodiments of the present invention provide
advantages of having multiple light sources that are arranged to have the
same path length for projecting the image. Embodiments provide advantages
in emitting a three-dimensional image usable with passive glasses.

[0030] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
invention. As used herein, the singular forms "a", "an" and "the" are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising," when used in this specification, specify
the presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of one
more other features, integers, steps, operations, element components,
and/or groups thereof.

[0031] The corresponding structures, materials, acts, and equivalents of
all means or step plus function elements in the claims below are intended
to include any structure, material, or act for performing the function in
combination with other claimed elements as specifically claimed. The
description of the present invention has been presented for purposes of
illustration and description, but is not intended to be exhaustive or
limited to the invention in the form disclosed. Many modifications and
variations will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the invention. The embodiment was
chosen and described in order to best explain the principles of the
invention and the practical application, and to enable others of ordinary
skill in the art to understand the invention for various embodiments with
various modifications as are suited to the particular use contemplated

[0032] The flow diagrams depicted herein are just one example. There may
be many variations to this diagram or the steps (or operations) described
therein without departing from the spirit of the invention. For instance,
the steps may be performed in a differing order or steps may be added,
deleted or modified. All of these variations are considered a part of the
claimed invention.

[0033] While the preferred embodiment to the invention had been described,
it will be understood that those skilled in the art, both now and in the
future, may make various improvements and enhancements which fall within
the scope of the claims which follow. These claims should be construed to
maintain the proper protection for the invention first described.